Add and ignore x-amz-api-version

Fixes #497.

src/main/java/org/gaul/s3proxy/AwsHttpHeaders.java

@@ -18,6 +18,7 @@ package org.gaul.s3proxy;
 
 final class AwsHttpHeaders {
     static final String ACL = "x-amz-acl";
+    static final String API_VERSION = "x-amz-api-version";
     static final String CONTENT_SHA256 = "x-amz-content-sha256";
     static final String COPY_SOURCE = "x-amz-copy-source";
     static final String COPY_SOURCE_IF_MATCH = "x-amz-copy-source-if-match";

src/main/java/org/gaul/s3proxy/S3ProxyHandler.java

@@ -163,6 +163,7 @@ public class S3ProxyHandler {
     /** All supported x-amz- headers, except for x-amz-meta- user metadata. */
     private static final Set<String> SUPPORTED_X_AMZ_HEADERS = ImmutableSet.of(
             AwsHttpHeaders.ACL,
+            AwsHttpHeaders.API_VERSION,
             AwsHttpHeaders.CONTENT_SHA256,
             AwsHttpHeaders.COPY_SOURCE,
             AwsHttpHeaders.COPY_SOURCE_IF_MATCH,